A pick-and-place machine and method includes use of a passive component feeder cartridge including a feeder gear. Rotation of the feeder gear causes a component-bearing tape to be fed through the feeder cartridge. A pickup head includes a vacuum nozzle to pick up the components from the tape and a rack gear to engage and drive the feeder gear of the feeder cartridge via translational motion of the pickup head when operatively disposed with respect to a selected feeder cartridge.
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59. A component feeder for use in a pick-and-place machine to incrementally advance a tape bearing a plurality of components, said component feeder comprising:
a body including spaced-apart engagement portions configured to respectively matingly engage a pair of extended parallel spaced-apart attachment structures of a feeder module or a pick-and-place machine to detachably connect the feeder to the feeder module or the pick-and-place machine, the spaced-apart engagement portions including at least one connecting structure configured to engage at least one of the attachment structures with a snap-fit; and
a mechanism mounted on the body, the mechanism being configured to engage and advance the tape bearing the plurality of components,
wherein the spaced-apart engagement portions are disposed on a same end-side of the body such that engagement with the pair of extended parallel spaced-apart attachment structure causes the body to be supported by the attachment structures at only a first end portion of the body such that the body extends therefrom in a horizontal orientation to form a cantilevered attachment.
13. A feeder module assembly for use in a pick-and-place machine, said feeder module assembly comprising:
a feeder module configured to interface with a pick-and-place machine, the feeder module including:
a frame configured to support a plurality of component feeders;
extended parallel and spaced-apart attachment structures disposed along a side of the frame that, in use, will be aligned with a pick-and-place machine, said attachment structures being configured for detachable connection thereto of plural component feeders to the frame; and
at least one component feeder configured to incrementally advance a tape bearing a plurality of components, the at least one component feeder including:
at least one connecting device configured to engage the attachment structures to detachably connect the at least one component feeder to the frame,
wherein the at least one component feeder is supported by the spaced-apart attachment structures of the frame at only a first end portion of the component feeder so as to form a cantilevered attachment wherein the feeder module does not support the component feeder from below.
1. A feeder module for use in a pick-and-place machine, said feeder module comprising:
a frame configured with a pair of extended parallel and spaced-apart support structures running in a first direction along the frame that will, in use, support plural component feeders and be aligned with a pick-and-place machine,
said spaced-apart support structures, in use, supporting a plurality of component feeders disposed in a second direction transverse to said first direction when each component feeder is snap-in connected to at least one of said spaced-apart support structures such that each component feeder is supported by said pair of spaced-apart support structures in cantilevered fashion, each one of said spaced-apart support structures being configured to simultaneously engage each component feeder of said plurality of component feeders when supported in cantilever fashion such that each component feeder (a) is supported by the spaced-apart support structures at only a first end portion thereof and (b) extends from said first end portion in a horizontal orientation;
a component supply portion configured to accommodate plural supplies of components, each supply being located below a respectively corresponding component feeder when in use; and
a lock mechanism configured to detachably connect the feeder module to a pick-and-place machine.
52. A feeder module assembly for use in a pick-and-place machine, said feeder module assembly comprising:
a feeder module configured to interface with a pick-and-place machine, the feeder module including:
a frame configured with a pair of extended parallel spaced-apart structures to support a plurality of component feeders, each one of said extended parallel spaced-apart structures being configured to simultaneously support each component feeder of said plurality of component feeders;
a component supply portion configured to accommodate plural supplies of components such that each supply is positioned below a respectively corresponding component feeder; and
at least one component feeder configured to incrementally advance a tape bearing a plurality of components, the at least one component feeder including:
a body, the at least one component feeder being configured to be snap-connected at only a single end portion thereof to said spaced-apart frame support structures so as to extend from the end portion in a horizontal orientation to form a cantilevered attachment, the body having an inlet formed therein that is adapted to receive the tape, the inlet being formed as an opening in a portion of the body that faces downwardly when the component feeder is supported by the frame such that the inlet and the respective supply are opposed to one another.
30. A feeder module assembly for use in a pick-and-place machine, said feeder module assembly comprising:
a feeder module configured to interface with a pick-and-place machine, the feeder module including:
a frame configured to support a plurality of component feeders;
an attachment structure configured for detachable connection of said plurality of component feeders to the frame, said attachment structure including a pair of extended parallel and spaced-apart attachment structures, each one of said extended parallel and spaced-apart attachment structures being configured to simultaneously support each component feeder of said plurality of component feeders; and
at least one component feeder configured to incrementally advance a tape bearing a plurality of components, the at least one component feeder including:
a body portion including spaced-apart engagement portions, the spaced-apart engagement portions including at least one connecting structure to engage the attachment structure of the frame in a snap-fit arrangement that detachably connects the at least one component feeder to the frame,
wherein the at least one component feeder (a) is supported by the extended parallel and spaced-apart attachment structures at only a first end portion thereof and (b) extends from said first end portion in a horizontal orientation to form a cantilever attachment.
47. A method of installing a feeder in a feeder module of a pick-and-place machine, the method comprising:
providing a feeder having a body portion with a first connector structure disposed at a lower end of the feeder body portion;
providing a feeder module having a first attachment structure configured for mating engagement with the first connector structure;
positioning the feeder on the feeder module for relative rotational movement at an upper end of the feeder body portion at a location spaced-apart from said first connector structure;
applying a downwardly-directed force to the body portion of the feeder at a location spaced-from said location thereby rotating the body portion of the feeder with respect to the feeder module to cause the first connector structure and the first attachment structure to engage one another in a snap-fit arrangement,
wherein the feeder includes a second connector structure at said upper end of the feeder body portion, the first connector structure and the second connector structure being disposed on a same end-side of the feeder, and
wherein engagement of the first connector structure with the first attachment structure and engagement of the second connector structure with the second attachment structure causes the feeder to be supported by the feeder module at only a first end portion of the feeder such that the feeder extends therefrom in a horizontal orientation to form a cantilevered attachment.
2. The feeder module of
3. The feeder module of
4. The feeder module of
5. The feeder module of
6. The feeder module of
7. The feeder module of
8. The feeder module of
9. The feeder module of
10. The feeder module of
11. The feeder module of
12. The feeder module of
14. The feeder module assembly of
15. The feeder module assembly of
16. The feeder module assembly of
17. The feeder module assembly of
the at least one connecting device of the at least one component feeder includes a first connecting device and a second connecting device,
the first attachment device and the second attachment device on the front plate portion being configured to respectively engage the first and second connecting devices of the at least one component feeder to detachably connect the at least one component feeder to the front plate portion in a snap-fit arrangement.
18. The feeder module assembly of
19. The feeder module assembly of
20. The feeder module assembly of
21. The feeder module assembly of
22. The feeder module assembly of
23. The feeder module assembly of
24. The feeder module assembly of
25. The feeder module assembly of
26. The feeder module assembly of
27. A pick-and-place machine for picking components from a feeder and placing the picked components onto a substrate, said machine comprising:
the feeder module assembly of
a pickup head including a pickup device adapted to pick up at least one component from a pickup zone and place the component onto a substrate.
28. The feeder module assembly of
29. The feeder module assembly of
31. The feeder module assembly of
32. The feeder module assembly of
33. The feeder module assembly of
34. The feeder module assembly of
35. The feeder module assembly of
36. The feeder module assembly of
37. The feeder module assembly of
38. The feeder module assembly of
39. The feeder module assembly of
40. The feeder module assembly of
41. A pick-and-place machine for picking components from a feeder and placing the picked components onto a substrate, said machine comprising:
the feeder module assembly of
a pickup head including a pickup device adapted to pick up at least one component from a pickup zone and place the component onto a substrate.
42. The feeder module assembly of
43. The feeder module assembly of
44. The feeder module assembly of
45. The feeder module assembly of
46. The feeder module assembly of
48. The method of
49. The method of
50. The method of
51. The method of
53. The feeder module assembly of
55. The feeder module assembly of
56. The feeder module assembly of
said at least one feeder including at least one connecting structure configured to engage the attachment structure to detachably connect the at least one component feeder to the frame.
57. The feeder module assembly of
58. The feeder module assembly of
60. The component feeder of
61. The component feeder of
63. The component feeder of
64. The component feeder of
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The present technology relates generally to the field of material handling, and more particularly to mechanisms and methods for transporting small articles from a first location to a second location, as might be involved during precise placement of components onto a printed circuit board.
Pickup, transport and precise placement of small articles normally includes use of a vacuum head for engaging and releasing the transported article. Such apparatuses are commonly referred to as pick and place mechanisms.
Some pick and place mechanisms include a pneumatic cylinder which drives a spindle mounting a vacuum head on a free end thereof. The spindle is advanced and retracted as required along its own axis, to pick up or place the articles (components), and is transported in a plane normal to the axis of the spindle to move the components from one location to another. Pneumatically operated devices are accompanied by substantial disadvantages inherent in pneumatic operation. Some drawbacks are the difficulty in monitoring the spindle position along its axis, and excessive size, particularly when the component is quite small.
Known pick and place mechanisms include, for example, U.S. Pat. No. 5,278,634 to Skunes, U.S. Pat. No. 6,145,901 to Rich, U.S. Pat. No. 4,860,438 to Chen, U.S. Pat. No. 4,595,335 to Takahashi, U.S. Pat. No. 4,151,945 to Ragard, U.S. Pat. No. 8,068,664 to Rudd and European patent application publication 0235045 A2 to Universal Instruments Corporation.
One exemplary pick-and-place machine feeds components from a supply tape cartridge advanced by a feeder gear mechanically rotated by the pickup head, thus avoiding the need for the tape cartridge to have on-board power components. The pickup head includes a pickup device (e.g., a vacuum nozzle) to pick up components from the tape as well as a rack gear to engage and drive the feeder gear of the supply tape cartridge. The pickup head also places components accurately on a substrate such as a printed circuit board (PCB).
The exemplary pick-and-place machine may include a component camera cooperating with a collimated light source arranged to project collimated light towards a component held by the pickup device and a diffuser screen disposed between the component and the component camera such that a shadow image of the held component is projected onto the diffuser screen. A linear correction and an angular correction of the held component position are calculated in accordance with this shadow image on the diffuser screen.
An exemplary pickup nozzle has an elongated hollow portion, a stop slidably disposed within the hollow portion, and a vacuum source in fluid communication with the hollow portion. The hollow portion is configured to simultaneously accommodate a plurality of picked-up components as the internal stop is adjusted in the proximal direction. A component can be ejected from the hollow portion and onto a substrate as the internal stop is adjusted in the distal direction.
A computer program readable storage medium may store computer program code structures including executable instructions that control at least one computer processor programmed to control a pick-and-place machine in picking up components from a feeder cartridge and then precisely placing the components onto a substrate (e.g., to assemble a printed circuit board). At least one pickup device may be selectively installed on the pickup head under such program control. Thereafter, the pickup head may be controlled to advance a selected component supply tape. A multi-purpose camera also mounted on the pickup head may read readable information on each feeder cartridge to obtain location and/or identification information for each respective feeder component and use such data to better insure correct assembly of the printed circuit board in accordance with the detected location and identification information.
Computer program code instructions may also control at least one processor in virtually assembling a printed circuit board with a plurality of components to be provided on a substrate at predetermined locations. Individual images of the plurality of components are overlaid on an image of the substrate in accordance with the predetermined locations. An operator may confirm the location of each virtual component placement to insure the proper location of each feeder without actually consuming any components.
A substrate having a plurality of components provided thereon (e.g., held on the substrate with soldering paste) can also be inspected. An imaging device may capture an image of each component on the substrate and then group the images such that images of what is supposed to be the same component type are grouped together so that one may readily detect whether in fact the components installed on the substrate (a) are the same component type; (b) are the intended component; and/or (c) were installed with the correct orientation.
An exemplary feeder cartridge for a pick-and-place machine may include a feeder gear which acts to feed a tape through the feeder cartridge, wherein the feeder cartridge itself is without onboard provisions of electrical, mechanical or pneumatic power.
An exemplary feeder module for a pick-and-place machine may be interchangeable with other feeder modules in the pick-and-place machine to reduce setup time. A user may configure in a feeder module a group of feeder cartridges for a particular job (e.g., assembly of a certain board) and leave the feeder module undisturbed until the next time that particular board assembly is needed. Such modularity may allow a user to change jobs in a matter of seconds.
Other aspects, features, and advantages of the present technology will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, which are a part of this disclosure and which illustrate, by way of example, different aspects of this technology.
The accompanying drawings facilitate an understanding of various embodiments wherein:
The following description is provided in relation to several examples (most of which are illustrated) which may share some common characteristics and features. It is to be understood that one or more features of any one example may be combinable with one or more features of the other examples. In addition, any single feature or combination of features in any of the examples may constitute additional examples.
1.0 Pick-and-Place Machine
The example pick-and-place machine shown in
Computerized control circuits are shown schematically in
CPU 110 also has control of various light sources (e.g., LEDs) and optical sensors 120 distributed throughout the pick-and-place machine 1000 as will be described further below. In addition, the exemplary pick-and-place machine 1000 also has a multi-purpose camera 252 and a component camera 251 interfaced with CPU 110 and utilized as explained below. Inductive coupling circuits 122 are also interfaced with CPU 110 and utilized to control optical interfaces with vacuum nozzles as will be explained. X/Y motor control 124 is also coupled to the CPU 110, as are control circuits 126 for controlling up/down pickup head motion and vacuum on/off valve control to the pickup head vacuum nozzle.
An X/Y motion system 400, shown in
Pickup head 200 is attached to a slider 455(1) that traverses a rail 423 parallel to the X axis. A motor 403 rotates a screw shaft 413 that also extends in the X axis direction. A nut member 455 receives screw shaft 413 and is also attached to slider 455(1) such that rotation of motor 403 causes movement of nut member 455 along the screw shaft 413, thereby causing the pickup head to traverse the rail 423 in the X axis direction.
Rail 423 is attached at its ends to respective nut members 445, 447. Nut members 445, 447 are each in turn connected to respective sliders 445(1), 447(1). The sliders 445(1), 447(1) are arranged for movement along respective parallel rails 424, 426 which each extend in the Y axis direction. Two parallel screw shafts 414, 416 are arranged along the Y axis direction such that each one of screw shafts 414, 416 extends through a respective nut member 445, 447. Each screw shaft 414, 416 is connected to a respective motor 404, 406 such that synchronous rotation of motors 404, 406 causes synchronized movement of nut members 445, 447 along screw shafts 414, 416, thereby causing rail 423 (and therefore pickup head 200) to move in the Y axis direction.
Rails 424, 426 may be positioned on support members 462, 464 to provide a stable, sturdy base for the motion system 400. Further, stabilizers 463, 465 may extend between and connect support members 462, 464 to prevent relative movement between the support members.
Motors 403, 404, 406 may be conventional synchronized incrementally stepped servo motors using encoders for conventional position feedback to enable precise positioning of pickup head 200 in the X/Y directions.
1.1 Feeder System
Now, with reference to
The handle portions 307 facilitate an operator in positioning the feeder module into, or removing the feeder module from, its operable position in the pick-and-place machine 1000. Feeder modules 300 are interchangeable. An alignment device (e.g., aperture 314) in front plate portion 306 is arranged to receive an alignment pin (not shown) that protrudes from pick-and-place machine 1000. The alignment pin serves to properly align feeder module 300 in the machine. The opposing end of front plate portion 306 may also include an aperture 314, as shown in
Alignment slots 398 may be spaced apart by 0.25 inches. A typical 8 mm tape feeder cartridge has a width of 0.5 inches, while 12 mm and 16 mm tape feeder cartridges have a width of 0.75 mm. Thus, by spacing the alignment slots 0.25 inches apart, 8 mm, 12 mm and 16 mm tape feeder cartridges can be accommodated without gaps or wasted spaced between the feeder cartridges.
The modular arrangement of feeder module 300 facilitates quick setup time. For instance, a user can configure in a feeder module 300 a group of feeder cartridges 350 for a particular job (e.g., assembly of a certain board). Feeder module 300 may be left undisturbed until the next time that particular board assembly is needed. Cost impediments to such strategy are removed by the relatively low cost of feeder cartridge 350, which is constructed from relatively inexpensive materials and designed without onboard provisions for power (as described below). In other words, a user can own significantly more feeder cartridges 350 as compared to conventional feeders without adding significantly to the cost of pick-and-place machine 1000. A user may even dedicate a feeder cartridge for each tape-wound reel 330. Feeder module 300 may accommodate up to 40 feeder cartridges, which may provide sufficient capacity for complex assemblies while also facilitating portability. However, feeder module 300 may be configured to accommodate more than 40 feeder cartridges depending on need.
An alternative feeder module 300-1 is shown in
Reel-retaining portion 309-1 may include support members (e.g., a pair of spaced support members 393 (e.g., a pair of rods)) to support reels 330, as best shown in
Feeder module 300-1 may include a locking device 391 to lock reels 330 in position in reel-retaining portion 309-1. Locking device 391 may include a locking member 394 (e.g., a rod or bar) positioned near a top portion of reels 330, a pair of triggers 395 on opposite ends of the feeder module to actuate the locking device, a pair of sleeves 362, a pair of springs 397 (e.g., a helical spring), and a pair of pivot arms 302 connecting locking member 394 to a respective trigger 395, as shown in
Locking member 394 may be connected to first end portions of pivot arms 302. Second end portions of pivot arms 302 may be rotatably connected to respective operating portions 395(2) via an optional block 396 as those skilled in the art will understand. Each helical spring 397 may extend between block 396 and sleeve 362 such that operating portion 395(2) extends through an inner portion of the helical spring. By this arrangement, spring 397 urges block 396 (and thus the second end portion of pivot arm 302 away from sleeve 362 (and toward front plate portion 306-1) thereby causing operating portion 395(2) to move toward front plate portion 306-1 and into an inserted position. When operating portion 395(2) is urged towards the front plate portion, locking member 394 is moved into a locking position, as shown in
Reels 330 may be easily inserted into reel-retaining portion 309-1 by pressing each reel against locking member 394 (when in the locked position) until locking member 394 is displaced against a restoring force of spring 397 a sufficient distance (
A user may pull trigger 395 away from front plate portion 306-1 against a restoring force of spring 397 to cause locking member 394 to be moved to the unlocked position shown in
It is noted that sleeve 362 may include an upright portion 362(1). In another example, the spring 397 may extend between the upright portion 361(2) and pivot arm 302 (e.g., via block 396). Those skilled in the art will understand and recognize that there are other suitable arrangements for arranging spring 397 in locking device 391. Furthermore, other suitable locking arrangements may be used to secure reels 330 in feeder module 300-1.
As shown in
Feeder module 300-1 may include rollers 301 configured to engage a surface of pick-and-place machine 1000 to facilitate insertion of the feeder module into an operative position in the pick-and-place machine. Apertures 304 (e.g., tapered bores) may be disposed at opposite end portions of the feeder module, as shown in
As shown in
The front plate portion 306 of frame 305 includes a first attachment device or connector (e.g., a protuberance 316, e.g., a rounded protuberance) along a side portion (e.g., a top edge portion) thereof and a second attachment device or connector (e.g., a recess 317) along a side portion (e.g., a bottom edge) thereof. It is noted that the first and second attachment devices may be partitioned (or otherwise divided) and thus each configured as a plurality of first attachment devices and a plurality of second attachment devices corresponding to a respective feeder cartridge. As mentioned above, alignment slots 398 are formed in an upper portion of front plate portion 306. In an example, the alignment slots may be at least partially formed in protuberance 316. Protuberance 316 and recess 317 facilitate attachment of a feeder cartridge 350 to front plate portion 306.
As best shown in
To mount feeder cartridge 350 to frame 305, upper attachment portion 352(1) may be placed over front plate portion 306 such that alignment protrusion 363 fits into a respective alignment slot 398 thereby positioning receiving portion 352(1)a around protuberance 316. A user may then press down upon knob 365 which causes inclined surface 352(2)b to engage front plate portion 306 (e.g., locating member 317(1)) which in turn causes lower attachment portion 352(2) to flex so as to cause projection 352(2)a to snap into recess 317 of front plate portion 306. The snap-fit arrangement of lower attachment portion 352(2) and recess 317 provides ease of installation. By this arrangement, feeder cartridge 350 is supported at only one end by the front plate portion 306 of feeder module 300 thereby forming a cantilever. This arrangement allows for compact feeder cartridge and reel packaging. The cantilever mounting of feeder cartridge 350 allows access to a bottom portion of the feeder cartridge. Therefore, reels 330 may be mounted below the feeder cartridges and the tape 340 from each reel may be fed to a bottom portion of a respective feeder cartridge. Providing the feeder cartridges and the reels in a stacked arrangement helps reduce the footprint of the feeder module. In another example, feeder cartridge 350 may be connected directly to pick-and-place machine 1000 in the manner of a cantilever. Preferably, receiving portion 352(1)a and the protuberance have mating shapes.
An example snap-fit arrangement may be described as “a mechanical joint system where part-to-part attachment is accomplished with locating and locking features (constraint features) that are homogenous with one or the other of the components being joined. Joining requires the (flexible) locking features to move aside for engagement with the mating part, followed by return of the locking feature toward its original position to accomplish the interference required to latch the components together. Locator features, the second type of constraint feature, are inflexible, providing strength and stability in the attachment,” The First Snap-Fit Handbook, Bonenberger, 2000.
To remove a feeder cartridge, a user may simply push upwardly upon knob 365 which causes front plate portion 306 to exert a force against lower attachment portion 352(2) which in turn causes the lower attachment portion to flex such that projection 352(2)a becomes disengaged with recess 317.
Referring to
Pick-and-place machine 1000 may include a detection device (e.g., an optical interrupter 313 provided on front plate portion 306) to detect the presence of feeder cartridge 350 in a properly installed position. Optical interrupter 313 includes spaced light emitting and light detecting portions as one skilled in the art will understand. A protruding portion 315 of body portion 352 is positioned to block the light transmission of optical interrupter 313 (thus triggering the optical interrupter) when feeder cartridge 350 has been inserted far enough that projection 352(2)a snaps into recess 317, thus confirming proper attachment of feeder cartridge 350 to front plate portion 306. A feeder cartridge 350 that is not inserted completely may have a raised position which may interfere with the pickup head. By the above described arrangement, feeder cartridge 350 will snap into place and be consistently positioned with respect to front plate portion 306 each time the feeder cartridge is connected to the front plate portion.
Optical interrupter 313 may be used to determine when a feeder cartridge 350 has been removed or when a new feeder cartridge has been added. As will be described later, the addition of a new feeder cartridge 350 may prompt pick-and-place machine 1000 to acquire information from the feeder cartridge.
In an alternative example shown in
Body portion 352 may further include a stabilizing portion 392 disposed between upper attachment portion 352(1) and lower attachment portion 352(2) and configured to engage front plate portion 306-1 to stabilize feeder cartridge 350. Stabilizing portion 392 may contact an engaging portion 367 of front plate portion 306-1 disposed between protuberance 316 and recess 317. Stabilizing portion 392 may include an extended flat portion configured to engage a flat portion of front plate portion 306-1 for stabilizing the feeder cartridge by limiting movement between feeder cartridge 350 and front plate portion 306-1. Those skilled in the art will recognize that other mating surfaces may be used to limit movement. Receiving portion 352(1)a-1 may include an extending portion configured to engage a surface of front plate portion 306-1 opposite protuberance 316.
Referring to
A feeder gear 355 is rotatably disposed in feeder cartridge 350. Feeder gear 355 is a passive gear relying on drive forces external of the feeder cartridge 350 for rotation. Feeder gear 355 may be exposed from body portion 352 to facilitate engagement with an external driving device. However, in another example, feeder gear 355 may be recessed into body portion 352 and accessible via a slot in the body portion. A sprocket wheel 356 (
Gear teeth 355(1) of feeder gear 355 engage cover film peeling gears 357, 358 (
As shown in
Turning back to
Now referring to
An alternative cover film drive assembly 370 is shown in
The second gear 372 may be supported on a tensioner arm 380. A lower portion of tensioner arm 380 includes a shaft opening 380(1) that rotatably receives shaft 382 (
The tensioner arm 380 may include a knob 380(3) to assist the operator in pivoting tensioner arm 380. Knob 380(3) protrudes upwardly from body portion 352 through opening 353 in the body portion.
In another example, first and second gears 371, 372 may each include separable portions, as shown in
Body portion 352 may include opposing curved portions 390 to assist in directing the cover film to cover film drive assembly 370. The curved portions may be tapered to more precisely direct the path of the cover film.
As shown in
Turning back to
Further, light pipe 354 of a feeder cartridge may blink (e.g., red) when the feeder cartridge will be empty in a certain amount of time (e.g., 20 minutes) at the current rate of production. The light may blink at a faster rate as the feeder cartridge approaches an empty status (e.g., 5 minutes until empty). This may alert a user to prepare a new reel of components for reloading, or the user may simply install a backup feeder cartridge to allow the machine to revert to the backup feeder cartridge upon depletion of the primary cartridge. Light pipe 354 of the primary feeder cartridge may then show red to indicate an empty status.
The feeder cartridge 350 parts (e.g., body portion 352, feeder gear 355, sprocket wheel 356, and cover film drive assembly 359, 370) are preferably formed of plastic (e.g., injection molded plastic).
1.2 Pickup Head
Referring to
A gear driving mechanism 210 is disposed at a lower portion of pickup head 200 and is rotatably connected to the front and rear lower wall portions 205, 207. As best shown in
A rack gear 216 is connected to the free ends of arms 212, 214 such that the rack gear extends between the arms. Rack gear 216 may be formed of any suitable material, but is preferably formed of aluminum, A1 stainless steel or brass. The rack gear has one or more gear teeth 216(1) that mesh with the gear teeth 355(1) of the feeder gear 355 of a particular feeder cartridge that happens to be aligned with it. That is, arms 212, 214 are configured to rotate downwardly to cause rack gear 216 to mesh with feeder gear 355 when the pickup head 200 is so positioned at a particular selected feeder cartridge 350, as best shown in
The gear driving mechanism 210 includes an optical sensing system (e.g., reflective sensors) to read the calibration marks 351 on the engaged feeder gear 355. In the illustrated example of
Optical sensors 218 may also be used to measure the gear position in the lateral (x) axis direction, as determined by a distance from one of the sensors 218 to feeder gear 355. Sensor 218 has a relatively narrow range (distance) over which the sensor can detect reflected light. The response signal amplitude peaks at a specific distance from feeder gear 355 and falls quickly at greater or lesser distances from that point thus making it possible to identify an optimal distance relative to the peak amplitude point. One skilled in the art will recognize that a “valley” instead of a peak of the signal amplitude may be used. Moving sensor 218 until the response has a predetermined amplitude relative to the peak amplitude will identify the lateral position of the gear (distance from feeder gear 355 to sensor 218). Since feeder gear 355, sprocket 356 and tape 340 are connected to one another, the measured lateral position of feeder gear 355 can be used to further determine the location of pickup zone 342 as well as a component to be picked. This peak/distance sensing operation may be done on the fly. For example, the process can be performed by starting with sensor 218 in relatively close position to feeder gear 355 and then moving the sensor away from the feeder gear, or alternatively, starting with sensor 218 relatively far away and then moving the sensor closer to the feeder gear, while noting a peak in the amplitude and the position where the peak occurred—the peak being at a known distance relative to a desired optimum distance.
The rotary position of feeder gear 355 can be used to determine component location in the Y axis direction, while the lateral position of the feeder gear can be used to determine component location in the X axis direction. This information is used by the pick-and-place machine 1000 to refine its determined location of pickup zone 342. Knowledge of the exact X axis location of pickup zone 342 can be used to mitigate or cancel the effects of feeder lateral location misalignment. Similarly, knowledge of the exact Y axis location of pickup zone 342 can be used to mitigate or eliminate the effects of errors caused by mechanical slop or lash in the drive gear train.
Sensor 218 includes an LED to emit light and a photosensor to detect the reflected light. However, one skilled in the art will understand that the LED may serve the dual functions of emitting light and sensing (now operating as a photodiode) reflected light. Such arrangement may reduce the space required by sensors 218 on the gear driving mechanism 210.
An electromechanical solenoid 220 is positioned in pickup head 200, as best shown in
Referring to
As shown in
Nozzle rotation motor 234 is positioned on a top side of platform 232 opposite nozzle holder 231. Nozzle rotation motor 234 serves to rotate vacuum nozzle 230 so as to adjust an angular position of a component picked-up/held by vacuum nozzle 230. Nozzle rotation motor 234 is preferably a servo step motor using a conventional position feedback encoder to provide precise rotary adjustment of vacuum nozzle 230.
Vacuum nozzle 230 is quickly raised and lowered by a crank mechanism connected to platform 232, e.g., via a force sensing mechanism 800 which will be described later. Crank arm 240 is connected to connecting rod 242 which extends downwardly to connect to platform 232. Crank arm drive 246 (e.g., a servo-controlled rotary motor) is arranged to rotate crank arm 240, thereby causing connecting rod 242 to raise or lower vacuum nozzle 230. When platform 232 is raised or lowered, nozzle rotation motor 234 is also raised or lowered along with platform 232. Platform 232 is arranged to slide along vertical guide rail 239 positioned on rear wall 204(1) of frame 204. Instead of a crank mechanism, vacuum nozzle 230 may be raised and lowered by other devices, such as a motor driven lead screw of a voice coil linear motor.
As can be seen in
As shown in
A nozzle changer cartridge 270 is shown in
The multi-purpose camera in pickup head 200 may be used to read the fiducial markings 233, 235 on vacuum nozzle 230 so as to selectively position the pickup head for pickup of a desired vacuum nozzle and/or for deposit of a vacuum nozzle in a currently empty position of the nozzle changer cartridge 270. CPU 110 may also be programmed to maintain a table or other data to record the identity of vacuum nozzles in particular changer cartridges positions, open positions in the changer cartridge, and the like.
Fiducial marks 271 (e.g., round dots) on the nozzle changer cartridge 270 are used to locate the precise installed location of the changer cartridge. Other information may be encoded by fiducial size or location, such as changer type, number of positions, etc. An optical interrupter (not shown) may be positioned internally to report when a user opens the changer cartridge 270 (e.g., to change the nozzle configuration). The system will be prompted to re-read fiducial markings 233, 235 on the vacuum nozzles if changer cartridge 270 is opened. Once the changer cartridge is open, the system may maintain the changer cartridge in the open position for the user's convenience.
1.3 Dual Camera Assembly
The pickup head 200 employs a dual camera assembly 250 to provide for component centering and a variety of other imaging control functions. Referring to
Component camera 251 and the multi-purpose camera 252 share a single lens 250(1) via beam splitter 250(2), as best shown in
The dual camera assembly 250 also comprises a conventional microprocessor/controller subsystem (not shown) and video capture hardware (not shown) to interface the cameras 251, 252 and the microprocessor/controller subsystem ultimately to the at least one system CPU 110.
1.3.1 Component Camera
Referring to
When the component C is picked up by vacuum nozzle 230, the vacuum nozzle is raised to the up position within pickup head 200, as shown in
A component C as held against the distal nozzle opening 230(3) is typically not exactly centered with respect to the nozzle opening. Thus, to ensure accurate placement of the held component on the substrate, an alignment correction must be calculated before the component is placed. The shadow image of the component on diffuser screen 259 is used to obtain this correction.
Squaring Method
In an example, a position adjustment routine, or “squaring method,” as described below with reference to
The component angle as actually held by the nozzle is measured by rotating the component C to a test angle of 22.5 degrees on either side of a nominal predetermined normal angle, as represented by steps 601, 602. Measurements begin with the narrow side of the component facing the camera. This orientation will result in the largest shadow length change for a given rotation. The squaring scale factor number is based on this orientation and the measurement does not work if the long dimension initially faces the camera. This problem does not exist with square symmetrical components. If the picked-up component is rotationally misaligned by 5 degrees, for example, the test rotations would yield actual orientation angles of 22.5-5 and 22.5+5 degrees, thereby resulting in component angles of 17.5 degrees and 27.5 degrees.
By measuring both directions a greater difference in the resulting silhouette length (angles) is available, which enhances precision. Because the ratio of these values is employed, the actual magnitude of these values, or in other words the size of the part, is irrelevant. In addition, this makes certain forms of image distortion and non-linearity self cancelling.
The ratio of the lengths of the horizontal shadows is related to the component angle. If the ratio is smaller than 1, the inverse of the ratio is used, and in either case, 1 is subtracted. This results in a number that increases as the component angle increases. The relationship to actual angle depends on the aspect ratio of the component (width/length), but is independent of size. The ratio is nearly proportional to angle, but has a small downward slope decreasing about 15% between 1 and 10 degrees. An equation is used to better fit the slope. For example, K-ratio*K/2.4+4.2 works well over a good range of component sizes, where K is the scale factor of a rotation of 10 degrees. The value K is typically 20-40 and may be calculated in advance if the component dimensions are known. The derivation process for K rotates the coordinates of the component as determined by the given dimensions (e.g., 10 degrees via trigonometry), then figures the ratio of the silhouette lengths and derives the scale factor that would convert the ratio to 10 degrees.
The component angle calculated by this procedure, as represented by step 603, will first be used to align the component to measure its linear misalignment. In step 604, the component is rotated back from the test angle (22.5 degrees) to the nominal predetermined normal angle (but in addition accounting for the calculated error angle) which aligns the narrower side of the rectangular component parallel to the camera. This rotational orientation is equivalent to an orientation the component would have had if the component was initially picked up with zero error. The left edge of the camera image is used as the reference point for measurements.
The fundamental unit of video measurement is the sensor pixel. A resolution of 0.001 inches per pixel is suitable. However, the measurement resolution is not limited to the size of a single pixel. The pixel intensity may be used to infer the actual edge position of the component, thus effectively increasing the available resolution. This is commonly known as sub pixel imaging, or sub pixel interpolation. To reduce the effect of “image noise,” measurements from several sequential lines may be averaged. In step 605, the pixel counts from the left edge of the image to both left and right edges of the component silhouette are measured. The center of the component is found by averaging these two values, in step 606. Center=(L+R)/2. The difference between the component center and the pickup spindle (nozzle holder) center is a linear error that must be corrected. In step 607, the component is then rotated 90 degrees and then, in step 608, the process is repeated to find the error on the other axis. The outcome of this process is both a linear X/Y correction and an angular correction, as represented by step 609. This will be applied to the spindle (nozzle holder) position just prior to the component being placed.
Averaging may be applied to the squaring process. That is, data from other scan lines in the component image may be employed. Specifically, several values of L from sequential scan lines may be averaged to produce a “cleaner” L. This process may also be used for R. Then, a single (L+R)/2 calculation may be performed, or alternatively, several (L+R)/2 calculations may be carried out with several raw L and R values, and then the (L+R)/2 results may be averaged to produce a cleaner (L+R)/2 result. When several data points are available, artifact rejection may also improve the quality of the resulting calculations. Data points that lie relatively far away from the others may be rejected as defective so as to not contaminate the result. This process can eliminate the influence of measurement noise or physical contamination such as dust in the image.
In addition to the center of the component, (R-L) may be calculated to determine the component length. Also, by counting the scan lines in the silhouette, the thickness of the component may be determined.
1.3.2 Multi-Purpose Camera
Referring to
The light that passes through beam splitter 260 may hit diffuser screen 259 and/or its mounting frame and be reflected back to beam splitter 260 which will reflect part of the light up to multi-purpose camera 252. The light being reflected off of diffuser screen 259 may create an undesirable ghost image on the diffuser screen which will overlay and interfere with the image of the substrate 258. In an example, an antireflective device (e.g., an antireflective coated circular polarizer 259(1)) may be installed between diffuser screen 259 and beam splitter 260. In the illustrated example, antireflective coated circular polarizer 259(1) is applied (e.g., glued) to diffuser screen 259. The antireflective coating prevents ghost reflections from its front surface as those skilled in the art will understand. The circular polarizer polarizes incoming light before it strikes diffuser screen 259. Thus, the light reflected off of diffuser screen 259 will have an opposite polarization to that allowed through the circular polarizer, thereby suppressing reflections.
Unlike the component camera 251, which may have a fixed focus due to its fixed vertical movement with the vacuum nozzle 230 (and therefore the imaged component), multi-purpose camera 252 has a variable focus due to its relative vertical movement with respect to substrate 258. The variable focus ability of multi-purpose camera 251 enables the camera to perform a variety of imaging functions.
Multi-purpose camera 252 is arranged to image the substrate (or vacuum nozzles, feeder cartridges, etc. located beneath pickup head 200). Multi-purpose camera 252 may also provide close-up images of components placed on substrate 258. Multi-purpose camera 252 may also image calibration marks provided on machine 1000 (e.g., on a base or support portion). Further, the camera can read barcode labels (e.g., label 361) on feeder cartridges 350. The multi-purpose camera 252 may also measure feeder cartridge 350 location targets (fiducial marks) (e.g., a round or square dot) on the feeder cartridge (e.g., on upper attachment portion 352(1)) to update the system with actual feeder location values. Each of these imaging functions is likely performed at a different focus distance.
Additionally, with a reverse periscope mirror system (not shown), multi-purpose camera 252 may serve the function of an up-facing component camera utilized to obtain alignment correction of component C. This is particularly useful for large integrated circuit packages (e.g., greater than 0.75 inch), which are typically imaged by an up-facing camera.
1.4 Force Measurement
Utilizing control of a “touch” force of nozzle 230 when picking or placing a component (part) allows significant advantages. Particularly, with a crank driven nozzle, the below described system allows a clean, “noise” free measurement of the actual force component of the crank drive movement. The oscillatory nature of the crank provides force in a constantly changing direction. Measuring stress in the crank arm itself would produce a value contaminated by force components that do not all operate on the part being picked or placed. Indeed, some of these force components are used to accelerate the crank system. The challenge ultimately amounts to isolating the vertical component from all of the other components and identifying an amount of the force that is contributing to acceleration/deceleration of the crank structure, and further, the amount of the force that is imparted to the picked or placed part itself.
The vertical component of force is isolated by a flexible mechanical structure akin to a door hinge, which is described below in relation to
A 3-axis accelerometer may be mounted on the moving structure to report vertical acceleration as an analog voltage. Thus, (acceleration) force may be derived from the acceleration using F=ma. The touch force is then calculated by subtracting the acceleration force from the total force. This measured force may be used to create a force-distance profile that can identify the absence or presence of solder paste, as described below in relation to
An example force sensing mechanism 800 is shown in
Attachment portion 806 is attached to platform 232, for example by screws extending through screw holes 806(1). Thus, circuit board 810 and housing 802 are permitted to move relative to one another by movement of flexing wall 807 via hinge 808. That is, for example, an upward force on nozzle 230 may cause housing 802 to move toward circuit board 810 as flexing wall 807 rotates outwardly. Such movement may be measured by force sensor 812 (e.g., a semiconductor and strain gauge on circuit board 810) to determine a magnitude of the upward force on nozzle 230. An adjustable member (e.g., a screw) may be attached to housing 802 and extend through aperture 816 to a position adjacent contact point 814 such that the screw presses upon contact point 814 when housing 802 moves closer to circuit board 810 to provide a force input to force sensor 812. Circuit board 810 may rest on a recessed portion 818 formed in attachment portion 806 such that the circuit board lies below platform 232.
As the nozzle is moved downwardly, housing 802 will tend to move away from circuit board 810, thus diminishing the measured force. On the other hand, when the nozzle is moved upwardly, housing 802 will tend to move toward circuit board 810 thereby increasing the measured force.
1.5 Laser Engraver
Pickup head 200 may also include a laser to engrave substrate 258 (e.g., PCB) with part information, date of manufacture, or other information.
Referring to
XY motion of pickup head 200 may be coordinated with ON/OFF beam modulation to draw symbols (e.g., alphabetic, numeric and/or barcode types). The laser energy could be linearly modulated or pulse width modulated proportionally to marking speed, however simple full ON or full OFF may be suitable.
The laser energy absorbed by substrate 258 may be used to vaporize or scar a PCB solder mask coating, PCB ink stencil markings, or apply a label to identify the board by marking thereon, e.g., the board type, revision, serial number, manufacturing date, machine operators name, and/or production lot. Barcode marking may be applied for subsequent reading by other machinery or hand held barcode readers.
Symbols could also be drawn by laser motion along one axis and board motion along the other axis by means of a board conveyor or by the normal use of the board motion axis where the pick and place machine moves the board along one axis and the head moves along the other axis. Alternatively, the pick and place machine may move the board in two axis directions and the laser could remain stationary.
Laser 900 could be mounted outside of pickup head 200. Additionally, the laser may be mounted on its own separate single or dual axis motion platform independent of the pickup head motion. The laser beam could be scanned with a rotating or oscillating mirror (e.g., galvanometer driven mirrors) to mark a board that is stationary or moving.
2.0 Operation
Operation of the example pick-and-place machine 1000 will now be described.
After the desired feeder cartridges 350 have been installed in pick-and-place machine 1000, pickup head 200 is moved to a position adjacent a feeder cartridge 350 having a component to be picked. Sensors 218 then scan the calibration marks on the feeder gear of the selected feeder cartridge. This position information is used to locate the feeder gear so that rack gear 216 can be aligned and engaged with the feeder gear. Such position information may also be used to determine a position of the component pockets on tape 340 if the calibration marks on the feeder gear are arranged to match the component spacing on tape 340. Next, gear driving mechanism 210 is lowered to cause rack gear 216 to engage feeder gear 355. Taking into account the position information of the feeder gear 355, motion system 400 then moves pickup head 200 a precise distance such that rack gear 216 drives feeder gear 355 to index (i.e., incrementally move) tape 340, thereby causing the next component pocket 343 to enter pickup zone 342.
After rack gear 216 is disengaged from feeder gear 355, the sensors 218 again detect the position of feeder gear 350 by sensing the calibration marks on the feeder gear. This position information is used to precisely locate the rotary orientation of the feeder gear and the component pocket locations for storage by CPU 110 and later use in subsequent “pickups.” Scanning calibration marks after the feed move substantially eliminates the negative effects of backlash. That is, if there is a discrepancy in actual distance moved and the intended distance of movement, such discrepancy can be corrected by a correction move in the Y direction. Gear driving mechanism 210 is then returned to its raised position (shown in
Next, the vacuum source is turned on and vacuum nozzle 230 is lowered into pickup zone 342 to contact or nearly contact a component positioned in a component pocket 343 in tape 340. Due to the vacuum force, the component is drawn up against distal nozzle opening 230(3).
The component is then imaged by component camera 251 and the above-described squaring method is performed to obtain and effect both a linear XY correction and an angular correction of the component held against the distal nozzle opening.
The vacuum nozzle is then positioned over the desired placement location (with both linear and angular corrections included) and lowered to place the component (e.g., by pushing the component into solder paste) on the substrate 258. The vacuum source is then turned off and vacuum nozzle 230 is raised leaving the component in place on the substrate. The pickup head is then moved to the feeder cartridge having the next component to be picked and placed. This process is repeated until all the desired components have been placed on the substrate. CPU 110 may store computer program code structures to carry out the example method of operation described above.
2.1 Control Computer Program Code Structures
The control program code structures 112, when executed by CPU 110, provide a system designed to simplify machine operation for the user. CPU 110 executes stored program code to provide advantageous set-up features.
2.11 Auto-Setup
An example automated set-up process will be described. Feeder management is often the largest part of the set-up process and an area where errors are frequently made. The disclosed exemplary auto set-up system significantly reduces set up time associated with assembling a new printed circuit board and eliminates many error-prone processes.
A user may install feeder cartridges 350 at any feeder module location in pick-and-place machine 1000. The feeder cartridges may be installed in full or half slots and may be placed in the machine without concern of the particular component (part) associated with a given feeder cartridge. Each feeder cartridge has a permanent alignment target mark (e.g., on upper attachment portion 352(1)) that when measured by multi-purpose camera 252 reports an exact location of the feeder cartridge. Further, each feeder slot may include an optical sensor to confirm proper installation of feeder cartridge 350 in pick-and-place machine 1000.
Multi-purpose camera 252 in conjunction with optical interrupter 313 will detect each feeder cartridge and determine the location of each feeder cartridge by its position (location information) in pick-and-place machine 1000. The multi-purpose camera 252 may also scan a machine readable barcode on label 361 which will inform CPU 110 of the particular component (e.g., identification information such as part number) associated with that feeder cartridge. As described earlier, the operator also may simply read the alphanumeric text on label 361 to ensure that the component identifying information (e.g., part number) on the label matches the component identifying information (e.g., part number) on reel 330 containing the tape being fed through the feeder cartridge, as a confirmation.
The system will then provide gathered feeder cartridge information to an assembly program which will identify any missing components. Should any components be missing, the user can simply add the missing feeder cartridges. The system will organize (e.g., schedule the picking and placing of each component) the assembly of the substrate in accordance with the location of each feeder cartridge and the identification information of the components. The system may also offer optimization suggestions (e.g., to reduce assembly time).
In order to recognize and identify any missing components, the system may compare the gathered feeder information against pre-defined PCB information The pre-defined PCB information may include a listing of each required component and coordinates for the placement locations of the components for a given PCB assembly. This information may be provided to CPU 110 to guide the assembly process. A comparison of the gathered feeder information and the pre-defined PCB may be displayed to an operator in the manner shown in
The system will also automatically select and install vacuum nozzles as needed. The vacuum nozzles 230 have machine readable identification information (e.g., a barcode) provided on an outer surface of the nozzles. Multi-purpose camera 252 is configured to read identification information on the vacuum nozzles and then automatically select the currently desired nozzle (e.g., from the nozzle changer cartridge 270) and install that nozzle on nozzle holder 231.
Additionally, the system provides flexible support for partial board population and various circuit board configurations. That is, for example, the user may activate or deactivate placement of a single component, multiple components or all components of a given part number.
Panel arrays are easy to setup and may be built in a variety of ways. It is often more efficient to build boards several at a time. The boards may be arranged in linear or rectilinear arrays. The user need only specify the spacing of the boards in the array and the system will perform the remaining set-up procedures. In a first example, the system may build complete boards one at a time. An advantage of this method is that the user may observe and inspect a complete board before building the other boards. This affords an opportunity to correct errors before building the other boards. In another example, the system may place each component of a given type and designation on all boards in the array before proceeding to the next component. This method is potentially faster because it may reduce the frequency of nozzle changes.
2.12 Virtual Build
As part of an initial set-up procedure, the system may provide a virtual build feature that enables a user to confirm component alignment in the feeder cartridges without wasting any components. A scanned image of the board (substrate) to be assembled, having no components yet placed thereon, as shown in
The system may use individual stored images (C1 to C8) of the actual components in each feeder cartridge, as shown in
In contrast to systems that create an image of the assembled board from imported data, the instant system does not presume a component orientation based on a user input (which if such input is incorrect results in a placement error). By using a captured image (including orientation) of the component on the tape, the possibility of user errors may be greatly reduced or even eliminated. In some machines, it is difficult to even see the component in the feeder. Further, determining an orientation of the component in such a machine may be further complicated by location (front, back, sides) of the feeder in the machine.
The virtual build process eliminates errors that have been common place. The results of the virtual build process may be presented to the user in a number of arrangements. In one example, a realistic view of the finished board is provided, as shown in
This system also logically facilitates the user in identifying the cause of errors. For example, if there is a problem with only a single component, the user may logically suspect that there is a problem with the CAD centroid data. If there is a problem with all of the components for a given feeder, then the user may logically suspect that the feeder cartridge data (e.g., part number, part value (e.g., 0.01 uF/20V), package number, feeder orientation, tape width/pitch, polar/non-polar(n/p)) is the likely cause. If rotation of the components appears to be correct at 0° and 180°, but wrong at all other angles, then the user may logically suspect that the rotation direction in the centroid data is backwards. If the location of some components is vastly wrong while the location of other components appears to be correct, then the user may logically suspect that the centroid data is incorrect. Further, if most or all of the component locations are off target by a considerable degree, the user may logically suspect that confusion in the unit of dimensions (e.g., inch/metric) is the cause. An advantage of the system is that these “diagnoses” are much more evident as compared to other systems.
Accordingly, a user may confirm placement of the various components against the pre-defined PCB data (described earlier). Unlike other systems, no components are consumed in this virtual process of confirming feeder cartridge installation and alignment. Feeder cartridge alignment may pertain to whether the cartridge in mounted in the front or back of the machine. Additionally, as described above, the virtual build process may also catch other errors such as erroneous CAD data and errors with incoming translations (e.g., unit of dimension, rotation direction, etc.). A user may correct an incoming translation error by applying a revised rule to the entire board to be assembled.
Additionally, the pre-defined PCB data may be represented graphically, as shown in
The system may also store the length, width and thickness of each component to later qualify each measured component as actually placed. This information may be used to test, adjust and perfect the video centering process. For instance, when a component is measured (during the linear/rotational error correction process), the component must meet dimensional specifications to prevent attempted placement of an out of position or missing component. Components identified as a “mis-pick” will be rejected and a full image of the component will be stored for troubleshooting.
2.13 Product Inspection
To facilitate finished product inspection, multi-purpose camera 252 may capture images of each component as it is actually placed on substrate 258. These images may be acquired after each placement or acquired sequentially after the entire assembly is complete. Acquiring an image after each placement requires less pickup head motion and is faster; however, if a subsequent placement interferes with a previous placement, the image of the previous placement would not show the subsequent movement of the component. So, capturing all of the images on a completed assembly is the most error free process, but is also more time consuming. However, the inspection phase causes pickup head motion only between nearby components, so the process is reasonably fast.
The system then organizes the images for easy inspection. For example, the images are rotated to the same orientation and then grouped (e.g., by part number). An example of such display screen is shown in
As shown in
As another finished product inspection procedure, the graphical representation of the pre-defined PCB (described earlier) may be overlaid onto an image of the actual finished PCB (e.g., captured by multi-purpose camera 252), as shown in
One skilled in the art will recognize that for each of the overlay procedures described above, either image may serve as the overlaid image. Further, those skilled in the art will also recognize that providing one or both images in at least partial transparency may facilitate comparison.
3.0 Multi-Component Vacuum Nozzle
Instead of the previously described vacuum nozzle 231, a multi-component vacuum nozzle system 500, shown in
Vacuum nozzle 502 is configured such that components enter the nozzle through distal nozzle opening 504. Vacuum nozzle 502 has a plurality of inner walls 507 forming a hollow portion 503, as best shown in
Stop 512 is slidably received in hollow portion 503. Four air passages 504(1), 504(2), 504(3), 504(4) are formed along respective corners of the hollow portion 503 to allow vacuum suction to pass around stop 512, as best shown in
In operation, the vacuum force draws a component into hollow portion 503 via the distal nozzle opening 504 so as to abut against stop 512. The stop 512 prevents the component from flipping. Once the component is established in place against the stop and between the inner walls 507, the stop is retracted into hollow portion 503 by a distance equal to the thickness of one component to make room for the next component. By providing a space at the end of hollow portion 503 that is only large enough for a single component, motion of the component is fully controlled. This process may be repeated to stack as many components as desired (e.g., up to 10 or more, 2-5, 5-10, 10-20, 15-20, up to 20, 20 or more) into hollow portion 503.
The stop 512 may later be moved toward distal nozzle opening 504 to push the components into the solder paste on the substrate. Stop 512 is preferably controlled by a servo step motor or a voice coil actuator with position feedback to enable precise incremental movements. Pickup head 200 may also incorporate a conventional force feedback measurement system to help guide the placement process.
3.1 Confirmation of Component Pickup
An optical sensor (e.g., LED/phototransistor sensor) 516 may be provided at an end portion of vacuum nozzle 502 to detect when a component has been successfully picked up. Sensor 516 is configured to emit a light beam from one side of the nozzle and to detect the light beam at the other side of the nozzle. When a component is successfully picked up, the component will block the light beam, thereby indicating a successful pickup. However, those skilled in the art will recognize that the sensor could depend on light reflection rather than light blockage in which case the sensor and emitter would be positioned on the same side of the nozzle. Additionally, mirrors, optical fibers, prisms, reflectors and/or light pipes may be used to transport light to/from stationary sensors/emitters on pickup head 200, thereby eliminating the need for inductive power transfer to sensors/emitters on vacuum nozzle 502. Further, other non-optical sensing methods may be employed. For instance, magnetic sensors that utilize induction or eddy current could be used, as well as other techniques such as ultrasonic detection, fluidic cross flow, air pressure or capacitance change. Cavity resonate frequency would change with component presence which could be detected in both acoustic and electromagnetic spectrums.
Further, as one skilled in the art will understand, an LED may be used both to emit light and to serve as a photodiode to sense light. Such dual function arrangement may reduce the space required by sensor 516 since an LED is typically smaller than a light-sensing photodiode or phototransistor.
An inductive coupling system is provided in the exemplary embodiment to provide power to illuminate the LED and to return an optical status signal over the inductive link. The inductive coupling system includes two coils that inductively couple without touching. Referring to
An example of a circuit for the inductive coupling system is shown in
The positive half phase powers the light sensing system. Either a phototransistor or an LED (PHOTO1) operating in photo sensing mode provides a signal that is amplified by a suitable transistor (Q1). This transistor draws more current when the sensor is illuminated and very little when the sensor is not illuminated. The magnitude of the current draw during the positive half phase reports the light/dark status of a light sensor. The shunt resistor (R1) in series with primary coupling coil 530 reports the LED drive current as a negative signal and the photo current as a positive one. A simple diode (right half of D1) separates the photocurrent from the LED current for easy measurement. Ultimately, the signal is conveyed as an analog level to a processor chip (e.g., CPU 110). The processor may note a light level just prior to beam blockage to reduce the effects of variation and drift. The processor may then set a threshold based on this value to reliably recognize small changes.
In another example, vacuum nozzle 502 may include a planar secondary coupling coil 522 (e.g., a planar spiral coil connected to or as part of flexible PCB 520) instead of the wire coil 510 for inductively coupling with primary coupling coil 530, as shown in
In another example, a vacuum sensor (not shown), instead of the optical sensor 516, could be provided near an end portion of vacuum nozzle 502 to confirm a successful pickup by detecting a change in pressure when a component occludes the hollow portion 503 thereby restricting vacuum flow.
3.2 Actuation of the Stop
A voice coil actuator may be employed to create a force to move stop 512 along hollow portion 503. A rare earth magnet 514 (e.g., 0.236 inches in diameter and 0.236 inches long) is attached to a magnet-receiving portion 513 at an upper portion of stop 512, as shown in
The space between linear drive coil 540 and magnet 514 may be as small as possible to optimize magnetic coupling. Linear drive coil 540 controls the position of the magnet 514 and the stop 512 with a magnetic field created by current flow in the linear drive coil, as one skilled in the art will understand. A suitable material for body portion 506 is carbon fiber. Current in linear drive coil 540 is preferably controlled by a class-D-amplifier with pulse width modulation.
Actuation of magnet 514 and stop 512 is preferably servo controlled to enable precise movements. The position of the magnet may be accurately determined with a magnetic field strength sensor. This technique is described in Honeywell application note AN211, which is incorporated herein by reference. The position may be reported magnetically as an analog voltage. This may be used in a proportional-integral-derivative (PID) servo loop to control the current in linear drive coil 540. Current in linear drive coil 540 may be adjusted as necessary to keep stop 512 in a desired position. Because the static magnetic field from magnet 514 and the dynamic field from linear drive coil 540 may both influence the magnetic field strength position sensor, position measurement requires measuring the static component from magnet 514 without outside influence. In order to achieve this, current in linear drive coil 540 may be turned off briefly during position measurement intervals. Several thousand measurements per second may be taken, as one skilled in the art will understand.
The combination of the voice coil actuator and the magnetic position feedback sensor provides very high resolution force measurement. Because the voice coil produces a force in proportion to drive current independent of magnet position over a modest range, the voice coil acts like a nearly linear spring. Thus, the voice coil actuator combined with the position sensor is somewhat analogous to a spring scale with milligram resolution. The system is adept at measuring force vs. distance relationships, since force is easily controlled as a direct function of current and distance is measured directly with the magnetic sensor. For relatively small parts, precision force control is essential to placing the parts without damage. It is noted that other feedback systems may also be used.
Vibration of stop 512 may be induced to aid in picking up and aligning components in the hollow portion 503. This vibration may be introduced as hysteresis in the servo loop to produce vibration at the update rate, or the vibration could be introduced as a separate error signal in the loop to obtain vibration at a lower frequency. The vibration may be turned on or off and the frequency and amplitude of the vibration may be changed to accommodate various components.
Additionally, optical sensor 516 may be used to confirm the location of the components held within hollow portion 503. The position of the components may be relative to a reference location such as the bottom of the last component picked up by vacuum nozzle 502. Thus, all movements of stop 512 may be relative to this reference location. This arrangement may diminish the need for accurate linearity over long travel distances of the magnet. This arrangement also mitigates variation in field strength of different magnets on different vacuum nozzles.
In an alternative arrangement, movement of stop 512 may be accomplished by a motor driven screw connected to the stop, as should now be appreciated by those in the art. A connection between stop 512 and the servo system is accomplished with a toroidal ring magnet on the outside of the body portion 506 that couples and captures a cylindrical magnet attached to the stop on the inside of the body portion. The stop is nonmagnetic to prevent flux from conveying down to the components. A rare earth magnet is used. The ring magnet and the cylinder magnet are magnetized along their lengths or thicknesses. These magnets are oriented so their opposing poles align and attract. While this coupling is compliant, it takes a large force to displace the magnet when captured inside the toroid. The magnetic coupling is essentially solid in the vertical displacement axis but allows friction-free rotation. The toroidal magnet is driven by a lead screw which is in turn driven by a gear and a long pinion. A servo or stepper motor may be used to control rotation of the lead screw and thus the vertical position of stop 512.
3.3 Operation
In operation of the example multi-component vacuum nozzle system 500, a calibration process is performed to set the position of stop 512 before a first component is picked from tape 340. Stop 512 is first lowered to break the light beam from sensor 516 and is then raised until the light beam is restored. This position of stop 512 may be a sufficient starting position for picking thin components; however, for thicker components, the stop may be raised further. Next, the vacuum source is turned on and vacuum nozzle 502 is lowered to nearly contact tape 340 between adjacent component pockets 343. Then, the vacuum nozzle is moved over a component pocket 343 to draw the component into the vacuum nozzle. A successful pick-up of the component is reported by sensor 516. Instead of sensor 516, it is noted that the previously described vacuum sensor may be used. Stop 512 is then moved up a distance equal to the thickness of a component in order to make room for the next component. Sensor 516 then reports that there is no blockage of the light beam. The vacuum nozzle is moved over the next component pocket 343 to pick the next component. This process may be repeated as necessary to pick a desired number of components. The tape may be indexed to bring the components to the vacuum nozzle 502 one at a time, or possibly, a large number of component pockets 343 may be simultaneously exposed in an elongated pickup zone so that the vacuum nozzle 502 can move across an exposed section of tape to rapidly pick up components. That is, each feed move may expose multiple components (e.g., 2-7, 7 or more, 10, 10 or more, 15-20, 5-15, 15 or more, 20, 20 or more).
If a component is unable to be picked by vacuum nozzle 502, the nozzle may re-try the pickup or go on to a subsequent component instead. Further, if the component ultimately is unable to be picked up by vacuum nozzle 502, the CPU 110 may keep track of such component and adjust the placement process accordingly so the nozzle does not attempt to place the (“missed”) component.
As described earlier, vibration of stop 512 may be induced to aid in picking up components. The stop may be lowered to a position near distal nozzle opening 504 and then a slight vertical vibration of stop 512 may be induced. The component would remain in motion after being drawn into hollow portion 503 due to the vibration of stop 512. However, in another example, the vibration may be stopped once the component is picked up. The stop is then moved up to confirm the component pickup and to make room for the next component. The vibration helps components find their way into and past distal nozzle opening 504, which for example may be a chamfered opening.
Once a desired number of components are loaded into hollow portion 503 of vacuum nozzle 502, the placement process may begin. The vacuum nozzle will be positioned over the first placement location and lowered to nearly touch substrate 258. Stop 512 is then lowered to push (or eject) a component out of nozzle opening 504 and into solder paste on the substrate. Once the component has been completely removed from vacuum nozzle 502, the vacuum force will be smaller than the adhesive force of the solder paste thereby causing the component to remain on the substrate as the vacuum nozzle 502 is raised. Because of the high bandwidth of motion of stop 512, components may be rapidly placed while pickup head 200 is still moving. Since slowing the pickup head to a complete stop consumes a great deal of time, keeping the pickup head moving at even a modest pace adds significantly to performance.
The stop positioning system can also report push force and distance with fine resolution, as described previously. Referring to
Additionally, sensor 516 may be used to confirm that a component was actually placed in the paste on the substrate. Stop 512 and the stack of components may be raised to confirm placement of a component by verifying that the light beam is not blocked. A component that will not remain on substrate 258 (e.g., because of missing paste) may be purged by placing the component in a dump area having an adhesive coated tape which retains the component.
While the examples discussed above have been described in connection with what are presently considered to be practical and preferred features, it is to be understood that appended claims are intended to cover modifications and equivalent arrangements included within the spirit and scope of these examples.
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